The present invention relates to a hydraulic control system for dividing hydraulic fluid flow between steering and auxiliary circuits, and more particularly, to a priority flow divider which provides full fluid flow to a steering valve when the valve is actuated, but when the valve is not actuated, the priority flow divider diverts all of the flow to an auxiliary circuit except for a small pilot flow.
It is common in earth-working equipment, such as backhoes, loaders, or the like, to have a bucket or shovel mounted on a tractor to be raised and lowered, tilted, or otherwise moved into the correct attitude by hydraulic cylinders supplied with fluid pressure from a suitable pump. The hydraulic systems for earth-working applications require a high volume of fluid at low pressure to rapidly move the cylindrical piston rods, and therefore, the bucket or shovel to the work.
It is conventional to provide a fluid flow divider between steering and auxiliary hydraulic circuits in fluid pressure operated load handling mechanisms such as earth-working equipment. Flow dividers have been used to provide a fixed amount of fluid flow to the steering circuit and to an auxiliary circuit. This permits the use of a fixed displacement pump for the auxiliary circuit to operate a backhoe or the like, and additional fluid flow is provided by the pump in the steering circuit to supplement the flow from the pump in the auxiliary circuit. A problem with known flow dividers is that they are not automatically actuated to provide full fluid flow to the steering valve when the valve is actuated and then divert the flow to the auxiliary circuit when the valve is not actuated.
Another problem with known flow dividers which only give a fixed ratio flow to steering and auxiliary circuits is that they are typically used with closed center steering valves or open center, five line steering valves (inlet, outlet, two steeing cylinder lines, and a pressure sensing line). Since it is economically desirable to also use a four line, open center steering valve in the steering circuit, there has been a need for a flow divider which can be used in connection with other types of steering valves than those taught by the prior art.
Thus, the disadvantages of present flow dividers for fluid pressure operated machines such as earth-working equipment have resulted in the priority flow divider of the present invention which provides full fluid flow to the steering valve when the steering valve is being actuated, but when it is not being actuated, all of the flow is diverted to an auxiliary circuit except for a small pilot flow.